Waste water purification apparatus and waste water purification method including the regeneration of used coagulant

ABSTRACT

Conventional purification apparatuses and operation methods therefor require continuous addition of coagulants as expendables in every operation, and the coagulants are expensive, thereby causing increase in operation cost, and furthermore, the operators have to convey and resupply the coagulant at regular intervals which further increases the operation cost owing to the personnel cost to be increased accordingly. The invention provides a purification apparatus and an operation method therefor, for coagulating and separating particularly the pollutant matter in sea water including oil and the like, which can regenerate and reuse the coagulant within the apparatus, without scarcely resupplying the coagulant and acid/alkali solutions. For disintegrating coagulated flocs and regenerating the coagulant from the sludge, a strong alkali solution and a strong acid solution are required. According to the invention, an alkali water enriched in sodium hydroxide and an acidic aqueous solution containing hydrochloric acid and the like are generated by electrolyzing sea water and collecting sodium ion and chloride ion respectively in the cathode and anode sections, and also by including hydroxide ion and hydrogen ion in sea water; the flocs in the sludge are disintegrated by use of the alkali water; pollutant matter is removed from the aqueous solution subjected to disintegration; and the strongly acidic solution containing hydrochloric acid is added to the acidic solution from which pollutant matter has been separated and removed, and a ferric chloride aqueous solution is generated. The ferric chloride aqueous solution is the coagulant, and thereby the coagulant can be regenerated from the recovered sludge.

TECHNICAL FIELD

The present invention relates to a waste water purification apparatusand an operation method therefor, which can reuse coagulants in arecycling manner and can dispose of recovered sludge satisfactorily.

BACKGROUND ART

Existing apparatuses for purification of polluted water, for example,include purification apparatuses and operation methods in which for thepurpose of filtering separation of pollutant particles of a few μm ormore in particle size or separating them according to specific gravitydifferences, a coagulant capable of supplying aluminum ion or iron ionis added to the polluted water as pretreatment for separation treatment,so that the pollutant particles are collected in the flocs whosematrixes are aluminum hydroxide and iron hydroxide, to form large anddense pollutant particle clumps of a few hundreds to a few thousands μmin particle size such that polluted water is purified through separationbased on filtration or specific gravity difference.

Also, included are purification apparatuses and operation methods inwhich a magnetic powder is added contemporarily with a coagulant to formthe magnetic flocs, and the magnetic flocs are trapped and separated byexerting magnetic force, so that polluted waster is purified. In thistype of purification apparatuses and operation methods, the metal ion inthe added coagulant is collected in the separated flocs or magneticflocs in the form of hydroxide, and the flocs are dehydrated with acentrifugal separator or a belt press machine and then subjected toincineration disposal, discard disposal, or composting disposal.

Accordingly, conventional purification apparatuses and operation methodsrequire continuous addition of coagulants as expendables in everyoperation.

However, the coagulants are expensive, thereby causing increase inoperation cost, and furthermore, the operators have to convey andresupply the coagulant at regular intervals which poses a problem thatthe operation cost is increased by the personnel cost to be increasedaccordingly.

Thus, in order to improve the efficiency in such a purificationapparatus and an operation method, as disclosed in JP-A-8-24515, theseparated matter obtained by coagulation and separation is first addedwith a strongly acidic aqueous solution such as sulfuric acid, so thatflocs or magnetic flocs are made to be situated in a strongly acidicsolution falling in the non-coagulation condition range, and the flocsare thereby disintegrated. Addition of a strongly acidic aqueoussolution such as sulfuric acid to this solution elutes the ions of suchmetals as aluminum from the metal hydroxides, forming an aqueoussolution of aluminum sulfate. The solution itself thus obtained is acoagulant, and can be reused as a coagulant.

Further, under this condition, the pollutant particles and magneticpowder are eliminated from the flocs, and the magnetic powder can bemagnetically separated by applying the magnetic force of a magnet,recovered, and reused.

Furthermore, the concentration of the pollutant particles can further beincreased by sedimentation, filtering separation with a membrane and thelike, and furthermore, by removal based on separation.

On the other hand, when the magnetic field is made extremely high by useof a superconductor magnet based on a super conductor bulk magnet or acoil type superconductor magnet as a magnet used for magneticseparation, if the iron based coagulant is used instead of a magneticpowder to form flocs on the basis of iron hydroxide, namely, the flocsare formed with weakly magnetic iron hydroxide, the flocs can bemagnetically separated without the use of the magnetic powder. In thiscase, accordingly a magnetic powder is not used, and hence no facilitiesfor supplying a magnetic powder and recovering the magnetic powder fromthe sludge are needed.

In the above described treatment method, in order to regeneratecoagulants an acid agent or an alkali agent is needed to be continuouslyadded as expendable, and hence there has occurred a problem that theoperation cost is increased by the cost defrayed for these two types ofreagents and by the personnel cost defrayed for the labor of theperiodic supply of these two types of reagents.

Further, in the case where the pollutant is crude oil, there occurs aproblem that the floc disintegration by acid or alkali treatment aloneallows the pollutant to remain mixed in the sludge so that the pollutantcannot be separated the from the sludge, and the regenerated coagulantis made to be mixed with the crude oil so that the coagulant cannot workas a satisfactory coagulant.

Furthermore, in the case where a purification apparatus is used on thesea-based platform for an offshore oil field, there occurs a problemthat the periodic supply of the coagulant requires the transportation bya helicopter or a devoted ship, which is accompanied by a hightransportation cost and a high unloading cost, thus resulting in anincrease of the purification operation cost.

Moreover, in the case where are removed the pollutant matters such asthe oil in the ballast water (For establishing the balance of a shipafter unloading, sea water is filled in the vacant space in the ship,and the sea water is discharged into the sea immediately beforeloading.) in a crude oil tanker, a natural gas carrying vessel, an orecarrying vessel, or the like, and the bacteria, plankton and the like inthe loaded sea water, periodic resupply of coagulants requires thepurchase of chemicals at the anchoring sites, and is accompanied with aproblem that the chemicals to be used are not easily obtainabledepending on the anchoring sites. Further, there occurs a problem thatharmful plankton in the separated or removed/recovered sludge cannot bedisinfected as the sludge remain separated so that the sludge is neededto be disinfected. Further, in the case where a volume reductionapparatus is needed to be installed for the recovered sludge, theinstallation space has to be secured, with an accompanying problem ofacquiring the space aboard.

DISCLOSURE OF INVENTION

An object of the present invention is to provide a purificationapparatus and an operation method therefor, which can regenerate andreuse the coagulant without resupplying the full quantity of anacid/alkali solution, and to provide a purification apparatus and anoperation method therefor, which can recover oil from the recoveredsludge and disinfect the pollutant matters.

The above described object is achieved by a waste water purificationsystem including a waste water purification apparatus which comprisespurification means for purifying the polluted water containingparticulate floating particles such as plankton, oil particles andorganic matters to be removed and the polluted water of factory effluentcontaining pollutant particles, phosphorus and the like to be removedthat are generated from industrial sites, means for recovering sludgethat is generated in the above described purification treatment, andmeans for discharging the purified water generated in the abovedescribed purification treatment. The purification means and the meansfor recovering sludge comprise coagulation and separation means forforming flocs containing pollutant particles, phosphorus and the like byinfusing coagulants, and for separating the flocs to generate purifiedwater, means for disintegrating the flocs collected as sludge by usingthe acidic solution and alkaline solution generated by electrolyzing theliquid, means for coagulant regeneration that extracts and separates thecoagulant in such a way that the device regenerates the coagulant fromthe substances forming the above described flocs and separates thecoagulant from the matters to be removed in the raw water, and sludgerecovering and discarding means for recovering and discarding the abovedescribed matters to be removed.

Also, the above described object is achieved by the waste waterpurification system in which the above described purification apparatuscomprises chemicals-free filtering means for physically filtering theabove described polluted water on the basis of a chemicals-freetreatment, and coagulation and separation means for separating the flocswhich are formed to contain pollutant particles, phosphorus and the likeby infusing a coagulant.

Further, the above described object is achieved by the waste waterpurification system in which the above described purification apparatuscomprises chemicals-free filtering means for physically filtering theabove described polluted water on the basis of a chemicals-freetreatment and coagulation and separation means for separating the abovedescribed magnetic flocs which are formed to contain pollutantparticles, phosphorus and the like by infusing a coagulant and amagnetic material, and thus magnetically separates and collects theabove described magnetic flocs as sludge.

Further, the above described object is achieved by the waste waterpurification system in which the above described liquid is sea water.

Furthermore, the above described object is achieved by the waste waterpurification system in which the above described liquid is soft wateradded with salt.

Moreover, the above described object is achieved by the waste waterpurification system in which the above described purification apparatuscomprises chemicals-free filtering means for physically filtering theabove described polluted water on the basis of a chemicals-freetreatment, and coagulation and separation means for separating the abovedescribed magnetic flocs which are formed to contain pollutantparticles, phosphorus and the like by infusing a coagulant and amagnetic material, thus magnetically separates and collects the abovedescribed magnetic flocs as sludge, disintegrates the above describedmagnetic flocs, and then recovers the magnetic material.

Additionally, the above described object is achieved by the waste waterpurification system in which the sludge, discharged from the sludgerecovering and discarding means that recovers and discards the abovedescribed matters to be removed, is introduced into a domestic wastewater purification means that treats the domestic sludge generated fromhuman domestic waste water including sewage.

Further, the above described object is achieved by the waste waterpurification system in which the above described waste wasterpurification apparatus further comprises means for centrifugalseparation of floating particles that centrifugally separates andrecovers floating particles after disintegrating the above describedflocs.

Further, the above described object is achieved by a waste waterpurification system that is arranged in a ship.

Further, the above described object is achieved by the waste waterpurification system that is arranged in a ship and purifies under sailthe ballast water in the ship.

Furthermore, the above described object is achieved by the waste waterpurification system in which the above described waste waterpurification apparatus comprises floc disintegration means fordisintegrating the above described flocs collected as sludge by use ofthe acidic solution and/or the alkaline solution generated byelectrolyzing sea water or by use of the acidic solution and/or thealkaline solution generated by electrolyzing the soft water obtained bymembrane treatment of soft water or sea water, produces alkaline waterenriched in sodium hydroxide as well as in the hydroxide ion in seawater by electrolyzing sea water to collect the sodium ions around thecathode, and making membrane separation of the above described seawater.

Moreover, the above described object is achieved by the waste waterpurification system that is arranged on a sea-based platform andpurifies on the platform the waste water created on the platform.

Also, the above described object is achieved by a waste waterpurification system including a waste water purification apparatus inwhich the waste water purification apparatus comprises purificationmeans for making purification treatment of the polluted water containingthe floating particles including plankton, oil particles, organicmatters and the like all to be removed and the polluted water of factoryeffluent containing pollutant particles, phosphorus and the like all tobe removed and generated from industrial sites, sludge recovery meansfor separating and collecting the sludge, generated by the abovedescribed purification treatment, from the waste water, and means fordischarging the purified water generated by the above describedpurification treatment. The above described purification means and theabove described sludge recovery means comprise coagulation andseparation means for forming flocs containing pollutant particles,phosphorus and the like by infusing a coagulant and creates purifiedwater by separating the above described flocs, floc disintegrating meansfor disintegrating the above described flocs collected as sludge byusing the acidic solution and/or the alkaline solution generated byelectrolyzing the liquid, coagulant regeneration means for regeneratingthe coagulant from the matter forming the above described flocs andseparating the coagulant from the matter to be removed in the raw waterto extract and separate the coagulant, fresh coagulant supply means forsupplying fresh coagulant in a parallel manner when coagulant isdeficient, and sludge recovery and discard device for recovering anddiscarding the above described matter to be removed.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow diagram showing the waste water purification systemaccording to an embodiment of the present invention.

FIG. 2 is a sectional view of a waste water purification apparatus inthe embodiment according to the invention.

FIG. 3 is an X-X section view of the waste water purification apparatusin the embodiment, shown in FIG. 2, according to the invention.

FIG. 4 is a flow diagram of an electrolysis device in the flow of thewaste water purification apparatus in the embodiment, shown in FIG. 1,according to the invention.

FIG. 5 is a flow diagram of a waste water purification apparatusaccording to another embodiment of the invention.

FIG. 6 is a flow diagram of an electrolysis device in the flow of thewaste water purification apparatus of the other embodiment according tothe invention.

FIG. 7 is a flow diagram showing yet another embodiment of theinvention.

MODES FOR CARRYING OUT THE INVENTION

An embodiment of the invention will be described below with reference toFIGS. 1 to 3. FIG. 1 is a flow diagram of a waste water purificationsystem in which the invention has been incorporated. FIG. 2 is anenlarged sectional view of the membrane separation apparatus shown inFIG. 1. FIG. 3 is a semi-sectional view of FIG. 2 as viewed from above.

In FIG. 1, the raw water of polluted sea water containing the pollutantmatter including oil particles, bacteria, plankton, and organic matterparticulates, all forming the matter to be removed, is drawn up into araw water storage tank 5 from the sea 1 by use of a pump 4 through aduct 2 and a filter 3 for removing large pieces of trash. Into the rawwater tank 5 are added a magnetic powder from a magnetic powder slurrytank 7 a that supplies an magnetic powder of triiron tetraoxide slurry,a pH adjusting agent either from a sodium hydroxide aqueous solutiontank 7 b that supplies an alkaline pH adjusting agent containing sodiumhydroxide or from a hydrochloric acid aqueous solution tank 7 c thatsupplies an acidic pH adjusting agent containing hydrochloric acid, acoagulant from a coagulant tank 7 d that supplies an aqueous solution offerric chloride to be used as coagulant, and a coagulation aid from apolymer tank 7 e, through a duct 8 a respectively through theintermediary of flow regulating valves 6 a, 6 b, 6 c, 6 d and 6 e, allthe tanks being situated within a seeding agent adjustment apparatus 7.

The raw water added with these chemicals is subjected to rapid stirringwith stirring blades 11 a driven to rotate by a motor 10 a of a rapidstirring tank 9 a. Then, a polymer agent is added into a slow stirringtank 9 b, through a flow regulating valve 6 e and a duct 8 d, from thepolymer tank 7 e that supplies the polymer agent reinforce the flocsgenerated with the aid of the coagulant, and is subjected to slowstirring with stirring blades 11 b (driven to rotate by a motor 10 b inthe slow stirring tank 9 b, to generate a pretreated water 12 thatcontains magnetic flocs ranging from a few hundreds microns to a fewmillimeters in size.

The pretreated water 12 thus generated is led into a purificationapparatus 14 through a duct 13 as indicated by an arrow A.

Description will be made below on the construction of a membranemagnetic separation apparatus 14 with reference to FIGS. 2 and 3.

First, in FIG. 3, a mesh 15 is constructed in a drum-like shape, withstainless steel thin wire, copper thin wire, polyester fiber or thelike, that forms a membrane having openings ranging from a few micronsto a few tens microns in opening size, and both ends of the mesh 15 arejointed to shells 16, 17 that have no openings. One of the ends isjointed to a flange 18 in an integrated manner, and the center of theflange 18 is jointed to a rod 19. The rotation of the rod 19 driven by amotor 20 causes to rotate the flange 18, the shell 16, the drum-likemesh 15 and the shell 17.

The shell 17 and a fixed flange 21 are integrated into one watertightpiece, a nozzle 28 integrated with the fixed flange 21, maintaining thewatertightness with the aid of ring-shaped sliding bodies 22, 23 made ofa polymer material small in sliding resistance, is supported by a casing27, and the fixed flange 21 rotates without wobbling of the rotationaxis.

In FIG. 2, the mesh 15 is placed inside the casing 27 of the waterpurification tank. The pretreated water 12 flows from the duct 13 intothe outside of the mesh 15, and the pretreated water 12 passes throughthe mesh 15. At this time, magnetic flocs 24 in the pretreated water aretrapped on the outer surface of the mesh 15, the water that passesthrough the mesh 15 and thereby separated from the magnetic flocs 24becomes purified water 25 and comes down to and stored in a purifiedwater tank 29 shown in FIG. 3 through the nozzle 28. The stored purifiedwater 25 is released into a water reservoir 1 shown in FIG. 1 from anozzle 96 shown in FIG. 3 through a pipe 26. The driving force thatmakes the pretreated water pass through the mesh 15 is the liquid leveldifference between the pretreated water 12 and the purified water 25.

On the other hand, the magnetic flocs 24 are filtered by water passingand thereby attached as deposited matter onto the outer surface of themesh 15 rotating clockwise along the direction of the arrow shown inFIG. 2, migrating to the vicinity of the water surface. A part of thepurified water 25 is led from a nozzle 97 via a duct 98 in the purifiedwater tank 29 shown in FIG. 3 to a pump 99 and is used as washing water.

The pressurized washing water is subjected to washing water flowregulation with a flow regulating bypass valve 101 equipped at a midwayposition of a pipe 100 and a flow regulating valve 103 equipped at amidway position of a pipe 102, both shown in FIG. 3, and transferredfrom a pipe 30 to a shower pipe 31 shown in FIG. 2, and shower water 32is sprayed from the holes of a shower pipe 31, along the direction fromthe inner surface to the outer surface of the mesh 15.

An electrolysis apparatus 105 is provided at a position branched from amidway position along a pipe 104 shown in FIG. 3, and a part of thepurified water is led into the electrolysis apparatus 105. The inletflow into the electrolysis apparatus 105 is regulated with a flowregulating valve 106 and the flow regulating valve 103.

FIG. 4 is a flow diagram of the electrolysis apparatus depicted in FIG.1.

In FIG. 4, the purified water introduced into the electrolysis apparatus105 is branched by a pipe 300, one flow of the branched flows ispressurized to the order of a few tens atm with a mump 301, and is ledinto a reverse osmosis membrane separator 303 through a flow regulatingvalve 302. Here, sodium (Na) ion and chloride (Cl) ion are filtered andthe treated water becomes a soft water which is pressurized to a few atmwith a pump 305 and led into an electrolysis tank 306 through a pipe304.

In the electrolysis tank 306, the soft water is introduced into thespace between diaphragms 307, 308 capable of passing ions, andelectrtolyzed by supplying electric current from an electric powersupply 311 to a positive electrode 309 and a negative electrode 310. Analkaline aqueous solution enriched in OH ion is generated through thediaphragm 307 in a space 312 around the positive electrode 309, while onthe other hand, a acidic aqueous solution enriched in H ion is generatedin a space 313 around the negative electrode 310 through the diaphragm308. Further, the soft water is sometimes used for preparation ofchemicals including polymer agents.

On the other hand, the rest of the purified water introduced into theelectrolysis apparatus 105 is branched by the pipe 300 and introducedinto an electrolysis tank 316 through a flow regulating valve 314 and apipe 315. In the electrolysis tank 316, the brine from the pipe 315 andthe sea water high in salt concentration discharged from the reverseosmosis membrane separator 303 and introduced from a pipe 320 through aflow regulating valve 319 are introduced into the space betweendiaphragms 317, 318 capable of passing ions. Further, a sea water higherin salt concentration than the usual sea water flows in.

In the electrolysis tank 316, electrolysis is conducted by supplyingelectric current from an electric power supply 323 to a positiveelectrode 321 and a negative electrode 322. An aqueous solution enrichedin Cl ion is generated through the diaphragm 318 in a space 324 aroundthe positive electrode 321, while on the other hand, an aqueous solutionenriched in Na ion is generated in a space 325 around the negativeelectrode 322 through the diaphragm 317.

The superfluous fraction of the highly concentrated sea water dischargedfrom the reverse osmosis membrane separator 303 is discharged through apipe 107 and a flow regulating valve 108 outside the electrolysisapparatus 105, for example, to the sea.

Incidentally, in the electrolysis apparatuses 306, 316, although notshown in the figure, a pipe for discharging the gas generated insideincluding hydrogen gas to the atmosphere is provided and a liquid leveldetecting device and an automatic valve are arranged so that theinternal liquid level position is regulated.

The alkaline aqueous solution enriched in OH ion and generated in thespace 312 passes through a pipe 328, the aqueous solution enriched in Naion and generated in the space 325 passes through a pipe 329, and bothsolutions merge with each other in a pipe 330 to make a Na(OH) solution,which is supplied from the electrolysis apparatus 105, through a flowregulating valve 331 through a pipe 330 connected to the outside, to thesodium hydroxide aqueous solution tank 7 b placed in the seeding agentadjustment apparatus 7.

On the other hand, the acidic aqueous solution enriched in H ion andgenerated in the space 313 passes through a pipe 332, the aqueoussolution enriched in Cl ion generated in the space 324 passes through apipe 333, and both solutions merge with each other in a pipe 334 to makea HCl solution, which is supplied from the electrolysis apparatus 105,through a flow regulating valve 335 through a pipe 334 connected to theoutside, to the hydrochloric acid aqueous solution tank 7 c placed inthe seeding agent adjustment apparatus 7.

Superfluous fractions of the Na(OH) and HCl aqueous solutions aredischarged from the electrolysis apparatus 105 to the outside throughpipes 336, 337, 338 and flow regulating valves 339, 340. Both solutionsare neutralized with each other to make a salt containing aqueoussolution and discharged.

Further, a Na(OH) or HCl aqueous solution with predetermined pH value ismade to flow in a pipe 104 from the pipe 336 or 337 through a flowregulating valve 326 or 327.

As shown in FIG. 3, this solution is supplied from the pipe 104 to thepipe 30 so that an alkaline water or an acidic water is mixed in thewashing water. The deposited matter accumulated on the inner surface ofthe mesh 15 is exfoliated by the shower water 32 and the surface of themesh 15 is renewed, the magnetic flocs 24 are made to go back to thewater surface of the pretreatment water 12. Further, at the same time,the organic matter accumulated on the mesh 15 is washed with thealkaline water contained in the shower water 32, and the microbesincluding bacteria and the like sticking to the mesh 15 are disinfectedby the action of the acidic water that is mixed intermittently, so thatthe proliferation of microbes is prevented on the mesh 15. Furthermore,the prevention of the proliferation of microbes leads to the preventionof the generation of mucous bodily fluids generated from the bodies ofmicrobes, and hence trapping and fixing of the pollutant particles ontothe mesh 15 ascribable to the bodily fluids can be prevented.

Here, the duct 30 shown in FIG. 3 is fixed to and supported by thecasing 27 with the brackets (not shown in the figure).

As shown in FIG. 2, the magnetic flocs 24 exfoliated from the membraneare suspended in the vicinity of the water surface, and when the flocs24 approach, for example, the magnetic generating means constituted witha permanent magnet 35 with a surface magnetic field strength of 0.5Tesla and a supporting frame 36, the flocs 24 undergo rapid magneticseparation and migrate toward the permanent magnet 35 owing to theexternal magnetic field gradient formed by the permanent magnet 35. Themagnetic flocs 38 that have migrated are attached to the surface of athin-walled shell 37, made of nonmagnetic stainless steel of a plasticmaterial, moving outside the magnetic field generating means.

As indicated by the arrow in FIG. 1, the magnetic flocs 38 attached ontothe shell 37 rotating anticlockwise are exposed to the atmosphere. Atthis time, superfluous water in the magnetic flocs 38 is separated bygravitation, and flow down on the surface of the shell 37 or drip downso that the magnetic flocs 38 are concentrated in the moisture contentto the order of 95%. The use of a coil type normal conduction magnet, acoil type superconducting magnet, a superconducting bulk magnet or thelike, in place of the permanent magnet 35, yields similar effects.

As shown in FIG. 3, one end of the shell 37 is jointed to a flange 39,and a rod 40 jointed to the flange 39 is rotated by a motor 41. The rod40 is supported by the casing 25, maintaining watertight with the aid ofan O ring 42. The motor 41 is fixed to and supported by the casing 25.The other end of the shell 37 is rotatably supported by the casing 27,maintaining watertight with the aid of an O ring 43, and the interior ofthe shell 37 is open to the atmosphere. The permanent magnet 35 is fixedto and supported by, with the aid of the supporting frame 38, by thecasing 25 with bolts or the like through the intermediary of a bracket44 a from the side of the atmosphere.

The construction described above permits easy arrangement of themagnetic field generating means from the outside. The motor 41 is fixedto and supported by the casing 25.

The concentrated magnetic flocs 38 on the surface of the shell 37 aremoved by rotation and get away from the magnetic field generating meansso that the magnetic attracting force becomes extremely weak, and hencethe magnetic flocs are exfoliated from the surface of the shell 37 witha plane knife 42 as a tool for scratching off, and separated andcollected as sludge into a sludge tank 43. The sludge in the sludge tank43 is transferred upward in FIG. 2, with the aid of a set of collectingplates 44 arranged in the bottom of the sludge tank 43 and jointed to arod 45 rotated by a motor 46, and discharged from an outlet 47. Thedischarged sludge is stored in a sludge tank 49 through a pipe 48 shownin FIG. 1. The sludge is transferred to a sludge decomposition tank 50a. In the sludge decomposition tank 50 a, added is the acidic aqueoussolution form the hydrochloric acid aqueous solution tank 7 c through apipe 50 b and a flow regulating valve 50 c.

When a prescribed acidity is attained, the flocs are disintegrated, andthe hydroxide having formed the flocs is decomposed in such a way thatiron hydroxide, for example, is decomposed into iron ion and hydroxideion. At this time, the matters to be removed, namely, the magneticpowder, oil particles, plankton, bacteria and the like, all having beencontained in the flocs, respectively remain in the sludge aqueoussolution in a mixed but separated manner. Further, the plankton andbacteria are disinfected with the acidic water and thereby annihilated.

In FIG. 1, the sludge aqueous solution is transferred to a magneticseparation tank 51 a, where the magnetic powder in the sludge aqueoussolution is magnetically separated and recovered with a permanent magnetor the like, and then the sludge is recovered through a pipe 51 b intothe magnetic powder slurry tank 7 a and reused.

The sludge aqueous solution that has been subjected to magnetic powderrecovery is introduced into a liquid cyclone tank 52 a, where the sludgeaqueous solution is separated into oil, organic matter, planktoncarcasses and the like. Here, the aqueous solution containing iron ionis recovered as coagulant, and transferred into the coagulant tank 7 dthrough a pipe 52 b. Further, the oil which is light in specific gravityis separated, and then discharged from a pipe 52 c to be recovered. Tothe aqueous solution containing organic matter and plankton carcasses isadded for neutralization a sodium hydroxide aqueous solution from thesodium hydroxide aqueous solution tank 7 b through a pipe (not shown inthe figure) and a flow regulating valve (not shown in the figure).

The aqueous solution is added polymer through a pipe 52 d and a flowregulating valve 52 e, and then concentrated with a centrifugalseparator, a belt press machine or the like, installed in a dehydrationapparatus 52 f, and transferred into a high concentration sludge tank 52h through a pipe 52 g. The separated clear supernatant liquid isdischarged from a pipe 52 j and returned to the raw water tank 5.

The sludge in the high concentration sludge tank 52 h is stocked fortransportation by truck to disposal sites or incineration sites, ortransferred to a composting tank provided in a later stage of processingwhere the sludge is composted.

On completion of composting, the compost may be pulverized into powderand the magnetic powder and produced magnetic matter may be recoveredfor reuse with another magnet type magnetic separating device.

Also, in the case where the apparatus concerned is placed in a humanresidential space area, it is often provided with a sewage purificationapparatus for treating human sewage, and the sludge in the highconcentration sludge tank 52 h can be led into the sewage purificationapparatus (not shown in the figure) and made to reduce the volumethereof through decomposition by microbes.

On the other hand, in FIG. 2, side walls 53 are arranged on both sidesof the knife 42 to prevent falling of the sludge inside the casing 27.The side walls 53 and the knife 42 are watertight against the casing 27,the edge of the knife 42 is pressed against the shell 37 with springs orthe like (not shown in the figure). The edge of the knife 42 is made ofa hard rubber.

A wall 54 is arranged which is made of a nonmagnetic material and fixedto and supported by the casing 27, for the purpose of preventingremoisturization of the magnetic flocs 38 caused by the splashing waterflow of the shower water 32 on the surface of the casing 37.

Further, a wall 55 which is made of a nonmagnetic material and fixed toand supported by the casing 27, is arranged in the lower part of theshell 37 so that the magnetic flocs 38 exfoliated from the mesh 15 byapplying the shower water 32 are not scattered away from the exfoliationlocation, but are made to suspend within the generated magnetic field,magnetically attracted and magnetically trapped on the surface of theshell 37.

Furthermore, a shower pipe 56 is arranged outside the mesh 15, and theouter surface of the mesh 15 is also washed with shower water 60 forrecovery. The shower pipe 56 is branched from the pipe 30 and suppliedwith shower water. Thus, the outer surface of the mesh is washed and theclogging of the mesh can be prevented.

Moreover, as for the level of the pretreated water 12, the signal from asupersonic type level gauge 200 is subjected to signal processing andtaken into a liquid level control apparatus 201; when the liquid levelof the pretreated water 12 exceeds the predetermined level, thefollowing control of the water level is performed: there is increasedthe number of revolutions of a motor 20 (depicted in FIG. 3) that iscontrolled in number of revolutions through an electric power line 202so that the staying time of the mesh 15 in the pretreated water isreduced, the filtration treatment amount of the mesh 15 is increased,and the water level of the pretreated water 12 is thereby made to belowered.

On the contrary, when the liquid level of the pretreated water 12depressed below the predetermined level, the number of revolutions ofthe motor 20 is decreased so that the staying time of the mesh 15 in thepretreated water 12 is elongated, the filtration treatment amount of themesh 15 is decreased, and the water level of the pretreated water 12 isthereby made to be raised.

In this connection, the operation generating the acidic water with theelectrolysis apparatus 105 shown in FIG. 3 may be continuous, orintermittent or periodic on a timer or the like. Further, for theelectric power source for electrolysis, a solar cell 109 or an electricpower line 110 may be used; the electrolysis apparatus may be providedwith a rechargeable battery (not shown in the figure), in which thepower fed from the solar cell 109 is stored and discharged forelectrolysis in rainy time.

Further, the hydrogen gas generated from the cathode of the electrolysistank 105 is led into the solar cell 201 through a pipe 200, the hydrogengas is allowed to react with the oxygen gas in the intake air togenerate electric power, and the electric power is fed into theelectrolysis apparatus 105 provided with electricity storage functionthrough an electric line 202; accordingly, the hydrogen gas generated inthe electrolysis tank 105 is effectively reused, leading to the effectthat the electric power consumption of the electrolysis tank can bereduced, and furthermore, the no release of hydrogen gas outside theapparatus leads to the effect that the danger of hydrogen explosion canbe prevented.

According to the above described embodiment, a part of the washing waterthat is sea raw water is lead into the electrolysis tank, where acidicwater and alkaline water are generated by electrolysis; the magneticflocs can be disintegrated by use of the acidic water so that themagnetic powder is recovered from the magnetic flocs to be reused, andfurthermore, the metal ion containing water to make coagulant can berecovered which can be used as a coagulant when used in combination withthe alkaline water. Further, resupply of magnetic powder and coagulantis scarcely needed, and the costs for chemicals and costs fortransportation of chemicals are almost vanishing, leading to the effectthat the operation cost can be reduced. Furthermore, the sludge isdisintegrated and the magnetic powder and coagulant are recovered, whichleads to the effect that the amount of generated sludge can be reduced.Additionally, the microbes in the sludge including bacteria can bedisinfected by the acidic water, which leads to the effect that theproliferation of bacteria can be prevented even if the sludge isdischarged into other oceans.

Further, the acidic water having disinfecting action is mixed in thewashing water, and the water permeable filtering separation membrane iswashed with the washing water continuously or at regular intervals;hence, the microbes including bacteria attached onto the mesh 15 isdisinfected by the disinfecting action of the acidic water, theproliferation of microbes on the mesh 15 is prevented, and the cloggingof the membrane is prevented, leading to the effect that the waterpermeability performance of the water permeable filtering separationmembrane is not degraded.

Moreover, the alkaline water having the action preventing the attachmentof the floating particles in the water is mixed in the washing water andthe water permeable filtering separation membrane is washed with thewashing water continuously or at regular intervals; hence, the cloggingof the membrane is prevented, leading to the effect that the waterpermeability performance of the water permeable filtering separationmembrane is not degraded.

Incidentally, in the embodiment, description has been made on thepurification apparatus in which the membrane filtering separation andthe magnetic separation are combined; however, in a purificationapparatus comprising membrane filtering separation, a membrane can begenerally applied to the purification apparatus for the purification,including the factory waste water purification and the sewagepurification, that use tap water or a part of the purified water as thewashing water for washing the membrane, also yielding similar effects.

Additionally, in the case where the raw water is soft water, continuoussupply of the salt (NaCl) to the electrolysis tank permits thegeneration of the acidic water and alkaline water, the recovery of thecoagulant from the magnetic flocs, and the reuse of the coagulant thusrecovered.

Further, in the above described embodiment, description has been made onthe case where a permanent magnet is applied for magnetic separation ofthe magnetic flocs; however, similar effects are obtained by use of asuperconducting bulk magnet o a coil type superconducting magnet inplace of the permanent magnet.

FIG. 5 illustrates another embodiment in accordance with the invention.FIG. 5 differs from FIG. 1 in that a device 340 for filtration withfilter sheet is provided for the purpose of separating relatively largeorganisms, for example, daphnias that cannot be incorporated into flocsby use of a coagulant in water. Such organisms are filtered with thefilter sheet of the order of a few hundreds microns in opening size inthe device for filtration with filter sheet. The relatively largeseparated matters that have been washed with the filter washing watercontaining a part of the filtrate water are mixed in the waste washingwater, and the waste washing water is made to reflow through a pipe 341to the raw water body. The filtrate water, from which particlesrelatively large in size are removed by the device 340 for filtrationwith filter sheet, is made to flow in the raw water tank 5.

According to this embodiment, the large organisms that are notincorporated into the flocs, generated after addition of the coagulant,can be removed beforehand, and hence floating particles of a fewhundreds microns or more in particle size can be removed beforehand, sothat the consumption quantity of the coagulant can be reduced, leadingto the effect that the operation cost can thereby be reduced.Additionally, the organisms that cannot be removed in the purificationtreatment are not discharged to the bodies of water other than that fromwhich the raw water is taken, leading to the effect that the disturbanceof the ecological systems, in the bodies of water other than the body ofwater from which the raw water is taken, can be prevented.

FIG. 6 illustrates the embodiment of another electrolysis apparatus 105in accordance with the invention. As shown in FIG. 6, the purified waterof sea water introduced into the electrolysis apparatus 105 ispressurized by a pump 401 through a pipe 300, and is led into anelectrolysis tank 406.

In the electrolysis tank 406, the purified water is introduced into thespace between diaphragms 407, 408, and electrolysis is made by supplyingelectric current from an electric power supply 411 to a positiveelectrode 409 and a negative electrode 410. Cl ion migrates into thespace 412 around the positive electrode 409 through the diaphragm 407,and discharging is made to generate chlorine gas. Accordingly, the space412 around the positive electrode 409 is saturated with chlorine gaswhich dissolves into the water to produce HCl and HClO, yielding anacidic aqueous solution.

On the other hand, around the negative electrode 410, OH ions and Naions are accumulated, with Na ions through the diaphragm 408, generatingan alkaline aqueous solution enriched in NaOH in a space 413.

The alkaline aqueous solution enriched in Na ion and OH ion generated inthe space 413 is supplied to the sodium hydroxide aqueous solution tank7 b equipped in the seeding agent adjustment apparatus 7 through a pipe414, a flow regulating valve 416, and the pipe 330 communicativelyconnected to the outside of the electrolysis apparatus 105.

On the other hand, the aqueous solution generated in the space 412,enriched in H ion, Cl ion and ClO ion, is supplied to the hydrochloricacid aqueous solution tank 7 c equipped in the seeding agent adjustmentapparatus 7 through a pipe 415, a flow regulating valve 417, and thepipe 334 communicatively connected to the outside of the electrolysisapparatus 105.

The acidic aqueous solution and alkaline aqueous solution, bothgenerated in a manner similar to that in FIG. 4, are mixed in thewashing water as alkaline water or acidic water, to be used forimproving the washing performance.

As shown in the flow diagram of the FIG. 4 the respective superfluousfractions of the Na(OH) and HCl aqueous solutions are neutralized witheach other to yield a salt containing aqueous solution, which isdischarged.

According to this embodiment, the electrolysis tank 406 is solelyinvolved in generation of the acidic and alkaline aqueous solutions,with which the coagulant can be regenerated, leading to the effect thatthe equipment cost can thereby be reduced.

Further, FIG. 7 illustrates yet another embodiment in accordance withthe invention, and differs from FIG. 1 in that: a fresh chemicalssupplying tank 500 is additionally equipped; a magnetic powder slurrytank 501 for supplying fresh magnetic powder and a coagulant tank 502for supplying fresh coagulant are equipped in the fresh chemicalssupplying tank 500; and fresh magnetic powder and fresh coagulant aresupplied, when chemicals supply is needed, respectively from themagnetic powder slurry tank 501 and the coagulant tank 502 through pipes505, 506 with the aid of flow regulating valves 503, 504, for thepurpose of making up the deficient amounts determined on the basis ofthe liquid level information obtained from the level gauges, not shownin the figure, equipped in the magnetic powder slurry tank 7 a andcoagulant tank 7 d, both used for recovery operation, and on the basisof the acidity information obtained from the pH meter equipped in thecoagulant tank 7 d and other like information. According to thisembodiment, for the case where the reuse ratios of the magnetic powderand coagulant do not reach 100%, fresh magnetic powder and coagulant canbe resupplied so that the coagulation performance can be maintained overa long period of time. When the coagulant is deficient, resupply of ironion, by the use of an iron electrode as an electrode in the electrolysisapparatus 105, can help maintain the coagulation performance over along-term period.

Further, in the above described embodiments, description has been madeon the cases where the acidic and alkaline waters, for disintegrationand recovery operation of flocs, are generated from electrolysis of seawater; however, generation of the acidic and alkaline waters from softwater also yields similar effects.

As having described above, according to the embodiments, a part of thewashing water that is the raw water is led into the electrolysis tankwhere the acidic and alkaline waters are generated by means ofelectrolysis; the use of the acidic water permits subjecting themagnetic flocs to disintegration and regeneration treatment in such away that the magnetic powder is recovered for reuse from the magneticflocs, and furthermore, metal ion containing water to be coagulant isrecovered; and the metal ion containing water can be used as coagulantwhen used in combination with the alkaline water. Accordingly, resupplyof magnetic powder and coagulant is scarcely needed, and the costs forchemicals and costs for transportation of chemicals are almostvanishing, leading to the effect that the operation cost can be reduced.Further, the sludge is disintegrated and the magnetic powder andcoagulant are recovered and reused, which leads to the effect that theamount of generated sludge can be reduced.

According to the invention, it is possible to provide a purificationapparatus and an operation method therefor, which can regenerate andreuse the coagulant without resupplying the full quantity of anacid/alkali solution, and it is also possible to provide a purificationapparatus and an operation method therefor, which can recover oil fromthe recovered sludge and disinfect the pollutant matters.

It will be further understood by those skilled in the art that theforegoing description has been made on the embodiments of the inventionand that various changes and modifications may be made in the inventionwithout departing from the spirit of the invention and the scope of theappended claims.

1. A waste water purification system including a waste waterpurification apparatus, wherein the waste water purification apparatuscomprises: purification means for purifying polluted water containingmatter to be removed including particulate floating particles such asplankton, oil particles, and organic matter, and polluted water formfactory effluent containing matter to be removed, generated fromindustrial production sites, including pollutant particles andphosphorus; sludge recovery means for separating and collecting, fromthe waste water, sludge generated in purification treatment; and meansfor discharging the purified water generated in the purificationtreatment; and said purification means and said sludge recovery meanscomprising: coagulation and separation means for forming flocscontaining pollutant particles, phosphorus and the like by infusing acoagulant, and for separating the flocs to create purified water; flocdisintegration means for disintegrating the flocs collected as sludge byuse of acidic solution/alkaline solution generated from electrolysis ofa liquid; coagulant regeneration means for regenerating the coagulantfrom matter forming the flocs, extracting and separating the coagulantby separating the coagulant from the matter to be removed in raw water;and sludge recovery and discard means for recovering and discarding thematter to be removed.
 2. A waste water purification system according toclaim 1, wherein said purification means comprises chemicals-freefiltration means for physically filtering the polluted water withchemicals-free treatment, and coagulation and separation means forforming flocs containing pollutant particles, phosphorus and the like byinfusing a coagulant and for separating the flocs.
 3. A waste waterpurification system according to claim 2, wherein said purificationmeans comprises chemicals-free filtration means for physically filteringthe polluted water with chemicals-free treatment, and coagulation andseparation means for forming magnetic flocs containing pollutantparticles, phosphorus and the like by infusing a coagulant and amagnetic powder, and for separating the magnetic flocs, wherein themagnetic flocs are magnetically separated and collected as sludge.
 4. Awaste water purification system according to claim 1, wherein saidliquid is sea water.
 5. A waste water purification system according toclaim 1, wherein said liquid is salt-added soft water.
 6. A waste waterpurification system according to claim 1, wherein said purificationmeans comprises chemicals-free filtration means for physically filteringthe polluted water with chemicals-free treatment, and coagulation andseparation means for forming magnetic flocs containing pollutantparticles, phosphorus and the like by infusing a coagulant and amagnetic powder, and for separating the magnetic flocs, wherein themagnetic flocs are magnetically separated and collected as sludge, themagnetic flocs are disintegrated, and then magnetic matter is recovered.7. A waste water purification system according to claim 1, wherein thesludge, discharged from the sludge recovery and discard means thatrecovers and discards the matter to be removed, is introduced intodomestic waste water purification means for treating domestic sludgegenerated from human domestic waste water including sewage.
 8. A wastewater purification system according to claim 1, wherein said waste waterpurification apparatus further comprises centrifugal separation meansfor centrifugally separating and recovering floating particles after theflocs have been disintegrated.
 9. A waste water purification systemaccording to claims 1 to 8, wherein the system is arranged in a ship.10. A waste water purification system according to claims 1 to 8,wherein the system is arranged in a ship, and purifies ballast water inthe ship under sailing.
 11. A waste water purification system accordingto claim 4, wherein said waste water purification apparatus comprisesfloc disintegration means for disintegrating the flocs collected assludge by use of acidic solution/alkaline solution generated fromelectrolysis of sea water and acidic solution/alkaline solutiongenerated from electrolysis of soft water or soft water obtained bytreating sea water with membrane, wherein sea water is electrolyzed tocollect sodium ion around the cathode, alkaline water enriched in sodiumhydroxide and hydroxide ion in sea water is generated, and the sea wateris subjected to membrane separation.
 12. A waste water purificationsystem according to claims 1 to 8, wherein the system is arranged on asea-based platform and purifies on the platform waste water created onthe platform.
 13. A waste water purification system including a wastewater purification apparatus, wherein the waste water purificationapparatus comprises: purification means for purifying polluted watercontaining matter to be removed including particulate floating particlessuch as plankton, oil particles, and organic matter, and polluted waterfrom factory effluent containing matter to be removed, generated fromindustrial production sites, including pollutant particles andphosphorus; sludge recovery means for separating and collecting, fromthe waste water, sludge generated in purification treatment; and meansfor discharging the purified water generated in the purificationtreatment; and said purification means and said sludge recovery meanscomprises: coagulation and separation means for forming flocs containingpollutant particles, phosphorus and the like by infusing a coagulant,and for separates the flocs to create purified water; flocdisintegration means for disintegrating the flocs collected as sludge byuse of acidic solution/alkaline solution generated from electrolysis ofa liquid; coagulant regeneration means for regenerating the coagulantfrom matter forming the flocs, extracting and separating the coagulantby separating the coagulant form the matter to be removed in raw water;fresh coagulant resupply means for supplying fresh coagulant whencoagulant is deficient; and sludge recovery and discard means forrecovering and discarding the matter to be removed.